1. Field of the Invention
The present invention relates to an image recording apparatus capable of efficiently recording a visible image on a recording sheet (recording medium).
2. Description of the Related Art
There has heretofore been known, for example, a thermosensitive or thermal transfer type image recording apparatus of a type wherein a recording head having a thermal head is moved in the direction which intersects the direction in which a recording sheet is fed, thereby recording a desired visible image on the recording sheet.
When a recording sheet (whose size is of, for example, A1 or A0) which is relatively large in size is used, the width of the recording sheet--i.e., the length of the recording sheet with respect to the direction in which the recording head is moved--is elongated, thereby causing the problem that the time required to record an image on the recording sheet is long.
In order to record the image on the recording sheet at a high speed, there has been proposed an image recording apparatus of a type wherein a plurality of recording heads are disposed in such a manner that they are spaced at predetermined intervals, and these recording heads are integrally moved in the same direction as the transverse direction of a recording sheet.
In such a conventional image recording apparatus, however, the plurality of recording heads are moved in the same direction as the transverse direction of the recording sheet. Therefore, the recording sheet is pressed by these recording heads, thereby allowing the recording sheet to be pushed in the direction of the recording heads. Thus, the conventional image recording apparatus has the problem that crumples or wrinkles are formed on the recording sheet so as to create an image-unrecordable portion thereof, so that an image recording process cannot be carried out with high accuracy.
There is also known an image recording apparatus of a type wherein while a pair of printing heads is being moved in such a manner as to approach each other from transversely-extending both sides of a recording sheet, the recording of an image from one end of the recording sheet to its central portion is carried out by using one of the printing heads, and thereafter the recording of an image from the central portion to the other end thereof is performed by making use of the other of the printing heads while the printing heads are being moved in the directions away from each other (see Japanese Patent Application Publication No. 56-10188). This image recording apparatus has, however, the problem that when it is desired to move the pair of printing heads in the direction to approach each other, the recording sheet can be bunched toward its center so as to form wrinkles thereon, thereby creating image-unrecorded portions on the recording sheet when it is desired to record the image on the recording sheet by one printing head referred to above. In addition, the image recording processes are alternately carried out by one of the printing heads and the other thereof as described above, thereby causing the problem that such image recording processes cannot be performed at a high speed.
In the thermal transfer type image recording apparatus, as well, a thermal transfer film is superimposed on a recording sheet while the thermal transfer film is being intermittently fed by a friction clutch of a feed mechanism. Under this condition, the recording head is used to record an image on the recording sheet.
However, when the delivery of the thermal transfer film is stopped, the tensile force exerted on the thermal transfer film is reduced, thereby often forming wrinkles or the like thereon. When the image recording process is done by using the recording head under this condition, there arises the undesirable condition that an image is not recorded owing to the presence of the wrinkles or the like, i.e., a so-called "void" occurs, thereby reducing the quality of an image.
Therefore, there has been proposed an image recording apparatus of a type wherein electric motors are respectively disposed on the side of a feeding unit for feeding a thermal transfer film to a recording head and on the side of a retracting unit for retracting the thermal transfer film from the side of the recording head, and these motors are energized to apply predetermined tension to the thermal transfer film (see Japanese Patent Application Laid-Open Nos. 61-11276 and 61-72570, for example).
However, in the conventional image recording apparatuses referred to above, there are disposed dedicated motors on the sides of the feeding unit and the retracting unit. Therefore, each image recording apparatus is rendered complex in structure, and the manufacturing cost of the entire apparatus is greatly increased.